Testimony of one witness regarding the credibility of another witness is impermissible. Additionally, the Court suggests that the trial judge should summarily cut off questions that elicit testimony on the credibility of a witness so that a jury is not contaminated by it.

Defendant appealed his jury conviction. Defendant was charged with one count of first-degree rape and two counts of first-degree sexual abuse of a child. No evidence of physical sexual abuse was found, however an interview performed by a pediatric nurse practitioner led to a diagnosis that sexual abuse had occurred. At trial, the nurse was asked "how" or "why" she was able to make such a diagnosis in this case. With regard to the victim, the nurse testified "there is no lying going on about what she is telling us in this evaluation." On appeal, defendant argued that admitting the diagnosing nurse's testimony was plain error because the testimony contained comments regarding the credibility of another witness. The Court agreed following State v. Lupoli, which held that a witness's testimony is impermissible when a witness comments on the credibility or truthfulness of another witness. Furthermore, the Court suggested that the trial judge, sua sponte, should have cut off questions attempting elicit the credibility of a witness before a jury is contaminated by it. Reversed and remanded.